Ampicillin is a beta-lactam antibiotic that has been used extensively to treat bacterial infections.

Ampicillin is effective against gram-negative organisms such as H. influenzae, coliforms and Proteus SPP.

As with other penicillin drugs, ampicillin is relatively non-toxic and adverse effects of a serious nature are rarely encountered.

Cloxacillin is a semisynthetic antibiotic in the same class as penicillin. Cloxacillin is used against staphylococci that produce beta-lactamase, due to its large R chain, which does not allow the beta-lactamases to bind.Cloxacillin has a weaker antibacterial activity than benzylpenicillin, and is devoid of serious toxicity except for allergic reactions.